23

Nov

Sheep scab can wreak havoc among your flock and decimate your profits. Unfortunately, the condition can be undetectable until it’s too late. Even worse, the misuse of treatments could lead to resistance. Here’s what you need to know.

SHEEP SCAB: DISGUISED TO THE EYES

Every farmer relies on their intuition now and again. But when it comes to the detection of sheep scab, intuition is an unreliable method. Once the scab mite finds its way to one of your sheep, it can take weeks or even months before the clinical signs are obvious. In short, you can’t tell whether your sheep are infected with scab simply by looking at them. Unfortunately that means many farmers are failing to take the necessary measures to protect their flock from the dangers of sheep scab.

KNOW YOUR ENEMY…

Sheep scab is caused by an infection with the mite Psoroptes ovis. The condition is endemic in the UK with around 10,000 cases per year – the increased movement and handling of sheep during autumn and winter is an added risk factor.

Sheep scab is an extreme form of allergic dermatitis caused by the faeces of the scab mite. Infestations can be highly debilitating and result in a significant loss of condition, secondary infections, hypothermia, and even death.

FIREFIGHTING IS INEFFICIENT

The unpredictable, often undetectable nature of sheep scab means that many farmers have a highly reactionary approach to controlling sheep scab. Unfortunately by the time you notice the clinical signs of sheep scab, the parasite will already have taken hold in your flock. That forces you into administering treatments that could have been prevented and having to observe the necessary meat withdrawal periods.

WATCH OUT FOR RESISTANCE

An ineffective strategy for the control of sheep scab has the potential to cause problems beyond economic inconvenience. The incorrect use of treatments can generate resistance in scab mites: for example, using diazinon plunge dip formulations with non-validated applications such as showers. Meanwhile the overuse of macrocyclic lactone (ML) injections for scab control can generate resistant gut worms as well as a potential for resistance in the scab mite itself, compounding the threat to sheep welfare on your farm.

A STRATEGY FOR MANAGING SHEEP SCAB

The safest and most cost-effective way to control sheep scab is to take a proactive approach, rather than waiting until the clinical signs are present on your farm. Given the difficulties of detecting the presence of sheep scab after initial infection, it’s always best to assume that all incoming sheep are infected and quarantine them for at least three weeks.

Additionally, testing sheep will allow you to ascertain their scab status and prevent unnecessary treatments.

Winter is generally the best time to treat your flock due to most farms retaining only breeding stock at this time of year. The full fleeces of your flock are also ideal for plunge dipping, arguably the most effective treatment for sheep scab.

Lack the facilities or finances for dipping? You can also tackle sheep scab with the correct injectables. It’s crucial to remember that all macrocyclic lactone treatments also act as wormers. Be sure their use is necessary and avoid repeat doses.

It’s also important to note that most MLs don’t offer persistent protection against scab. Following treatment with a non-persistent ML, move your flock to pasture that has been free of sheep for a minimum of three weeks. Scab mites can survive in the environment for up to 17 days.

If that’s not possible, consider using CYDECTIN® which offers persistent protection for 28 days or 60 days, depending on the strength of the dose. This allows you to move sheep to fields that have been recently grazed and avoiding potential worm issues with dosing and moving to clean pasture.

OVER TO YOU…

Sheep scab can be an annoyingly persistent problem. Many farmers across the UK struggle with the parasite, which can result in problems with sheep welfare and a negative impact on your bottom line. Yet with a front-foot approach to prevention and a proactive treatment strategy you can ensure your flock remains healthy, happy and profitable. As ever, if you are in any doubt consult your vet or medicine supplier.

Dave ArmstrongBVM&S CertSHP MRCVS

Dave is an RCVS advanced practitioner in Sheep Health and Production. He qualified from the Royal (Dick) Veterinary College in 2004, working mainly as a production animal veterinary surgeon, until joining Zoetis (previously known as Pfizer Animal Health) in 2010 as an Area Veterinary Manager. In 2015 Dave joined the Zoetis National Veterinary Manager team.

Dave’s areas of interest are the health and production of sheep and the sustainable control of parasites in farm animals. He is the chair of the NOAH anti-parasitics committee and sits on various national cross industry bodies including the sustainable control of parasites in sheep (SCOPS) board.

Dave is from a farming background and still manages his own flock of pedigree Texel and commercial mule sheep on the Welsh-Shropshire border.